src: use unique_ptr for internal JSON trace writer

PR-URL: #21867
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Author: addaleax

src/tracing/node_trace_writer.cc

@@ -37,9 +37,7 @@ void NodeTraceWriter::WriteSuffix() {
   {
     Mutex::ScopedLock scoped_lock(stream_mutex_);
     if (total_traces_ > 0) {
-      total_traces_ = 0;  // so we don't write it again in FlushPrivate
-      // Appends "]}" to stream_.
-      delete json_trace_writer_;
+      total_traces_ = kTracesPerFile;  // Act as if we reached the file limit.
       should_flush = true;
     }
   }
@@ -111,7 +109,7 @@ void NodeTraceWriter::AppendTraceEvent(TraceObject* trace_event) {
     // to a state where we can start writing trace events to it.
     // Repeatedly constructing and destroying json_trace_writer_ allows
     // us to use V8's JSON writer instead of implementing our own.
-    json_trace_writer_ = TraceWriter::CreateJSONTraceWriter(stream_);
+    json_trace_writer_.reset(TraceWriter::CreateJSONTraceWriter(stream_));
   }
   ++total_traces_;
   json_trace_writer_->AppendTraceEvent(trace_event);
@@ -126,7 +124,7 @@ void NodeTraceWriter::FlushPrivate() {
       total_traces_ = 0;
       // Destroying the member JSONTraceWriter object appends "]}" to
       // stream_ - in other words, ending a JSON file.
-      delete json_trace_writer_;
+      json_trace_writer_.reset();
     }
     // str() makes a copy of the contents of the stream.
     str = stream_.str();

src/tracing/node_trace_writer.h

@@ -63,7 +63,7 @@ class NodeTraceWriter : public AsyncTraceWriter {
   int file_num_ = 0;
   const std::string& log_file_pattern_;
   std::ostringstream stream_;
-  TraceWriter* json_trace_writer_ = nullptr;
+  std::unique_ptr<TraceWriter> json_trace_writer_;
   bool exited_ = false;
 };